How does the fixing rafters to the beams ?

mount trusses to beams as the best design option

to his home, you can use two types of roof systems - Hanging and inclined, each of which has certain advantages.So, Hanging farm are used more for the construction of a large area of ​​the roof light while slanted considered more thorough and easier to style, because each rafter "legs" in this case, two points of support, while the suspension is only one - the wall.

We are more interested in hanging version is more suitable for the attic.Simple assembly of roof frame of this type - on the basis of horizontal beams, which are placed on the edge of the wall, perpendicular to them.The beams are cut close to the ends of the grooves, recesses into which are inserted and rafters.

laid on top of the wall beam should project beyond the construction of up to 40 centimeters for the accuracy of the projections are measured only extreme beams, between which is stretched a string and have it carried out by laying the remaining crosspieces.

Of course, the grooves can not possibly keep quite heavy rafters, so they additionally fixed with special metal fasteners or, easier and more reliable, straps made of boards between the beam and rafter foot.In fact, the bar plays the role of connecting tightening element, reducing the compressive load.These spacers are installed and when the cross bar is not used in the design and rafters supported by mauerlat.

Sometimes such tightening is made of metal, especially if it is obvious that the roof load is large, or use a pre-stressed beams for rafters, that is reinforced napruzhinennymi flexible elements.If you plan to build attic, tightening can be a part of the overlap, ie logs, for which they are arranged in the lowest part of the rafters, exactly where the beams should lie.

As a combined floor joists and rafters?

As already mentioned, Hanging rafters are often based on the cross-beam from the beam, which in turn are placed directly on the wall.However, this design has a pressure point to a specific section of the wall, and so this method of construction for the roof trusses is acceptable only for wooden log cabins.

If the house is built of brick, with unallocated pressure on the walls of the edge begins to crumble in places boards location.It is in order to disperse the pressure on the wall, used mauerlat - thick beams to be placed along the wall crest.

In general, it turns out that mauerlat lie joists and rafters, and the first stacked close to the beam truss supports, thus creating unbroken surface of the overlap.Experienced masters recommend to use mauerlat bar section of 150x150 millimeters.

such dimensions is enough to discharge element to the edge of the walls will not warp under the weight of the roof.For more coverage of the walls can be installed reinforced belt, to which attach mauerlat corners.

approximate calculation of trusses, beams and span values ​​

Before erect roofing framework, it is necessary to find out, as precisely as possible, any snow load may please you weather to settle in the area.On the basis of data and should do the calculation rafters, roof beams and trusses elements that will hold the roof.In particular, you must make the structural calculations for the different sections of the wooden or metal frame elements, determine the amount of hops between the rafters and the thickness of the beams.

So, at a pressure of snow cover in the range of 1.5 kPa, and the cross-section trusses Softwood 38h140 at step between the "legs" of 300 mm span of the roof must not exceed 4.28 meters.Such data is easy to find on the Internet in the form of tables.

By the way, a step between the rafters may be different, but it depends on him the value of the span roof structure. Span - not that other, as the distance between the pillars that support the ridge beams.If they do not exist, it is considered to span the entire distance between the extreme rafters.

From this distance, by the way, may depend on the entire roof structure, as if the passage of 4.5 meters, for the construction of roof beams are used, while for large values ​​of the practical application of the farms.Sloping rafters more convenient when flying to 6.5 meters, and 7 meters of the roof is performed already on the hanging structure.